swscale: use SwsContext for av_log when available

Signed-off-by: Diego Biurrun <diego@biurrun.de>

libswscale/utils.c

@@ -787,11 +787,11 @@ int sws_init_context(SwsContext *c, SwsFilter *srcFilter, SwsFilter *dstFilter)
     unscaled = (srcW == dstW && srcH == dstH);
 
     if (!isSupportedIn(srcFormat)) {
-        av_log(NULL, AV_LOG_ERROR, "swScaler: %s is not supported as input pixel format\n", sws_format_name(srcFormat));
+        av_log(c, AV_LOG_ERROR, "%s is not supported as input pixel format\n", sws_format_name(srcFormat));
         return AVERROR(EINVAL);
     }
     if (!isSupportedOut(dstFormat)) {
-        av_log(NULL, AV_LOG_ERROR, "swScaler: %s is not supported as output pixel format\n", sws_format_name(dstFormat));
+        av_log(c, AV_LOG_ERROR, "%s is not supported as output pixel format\n", sws_format_name(dstFormat));
         return AVERROR(EINVAL);
     }
 
@@ -807,12 +807,12 @@ int sws_init_context(SwsContext *c, SwsFilter *srcFilter, SwsFilter *dstFilter)
                 |SWS_SPLINE
                 |SWS_BICUBLIN);
     if(!i || (i & (i-1))) {
-        av_log(NULL, AV_LOG_ERROR, "swScaler: Exactly one scaler algorithm must be chosen\n");
+        av_log(c, AV_LOG_ERROR, "Exactly one scaler algorithm must be chosen\n");
         return AVERROR(EINVAL);
     }
     /* sanity check */
     if (srcW<4 || srcH<1 || dstW<8 || dstH<1) { //FIXME check if these are enough and try to lowwer them after fixing the relevant parts of the code
-        av_log(NULL, AV_LOG_ERROR, "swScaler: %dx%d -> %dx%d is invalid scaling dimension\n",
+        av_log(c, AV_LOG_ERROR, "%dx%d -> %dx%d is invalid scaling dimension\n",
                srcW, srcH, dstW, dstH);
         return AVERROR(EINVAL);
     }